1. Field of the Invention
The present invention relates to an electromagnetic valve and, more particularly to an electromagnetic valve capable of functioning as an expander.
2. Description of the Related Art
In recent years, an air conditioner of heat pump type is proposed as an automotive air conditioner. In this air conditioner, a cycle operation using a refrigerant is carried out not only for the cooling but also for the heating, and a vehicle's passenger compartment can be dehumidified and heated. Such an automotive air conditioner has a refrigeration cycle including a compressor, an external heat exchanger, an evaporator, an internal heat exchanger and so forth. The functions of the external heat exchanger are switched between when the air conditioner is in a heating operation and when it is in a cooling operation. At the time the air conditioner is in the heating operation, the external heat exchanger functions as an evaporator. At this time, the internal heat exchanger radiates heat in a process where the refrigerant circulates in the refrigeration cycle, and the thus radiated heat heats air inside the passenger compartment. At the time the air conditioner is in a cooling operation, the external heat exchanger functions as a condenser. At this time, the refrigerant condensed by the external heat exchanger is evaporated by the evaporator, and the evaporative latent heat cools the air inside the passenger compartment.
In such an automotive air conditioner as described above, an expander is installed upstream of the evaporator. To facilitate the evaporation of the refrigeration by the evaporator installed downstream of the expander, the expander throttles and expands the refrigerant from an upstream side and delivers it to a downstream side by turning it into a spray. For such an expander as described above, an expansion valve, whose valve opening degree can be varied, an orifice, whose valve opening degree is fixed, and so forth are generally employed. As for the external heat exchanger, however, a relatively large flow rate of refrigerant needs to be ensured when the external heat exchanger functions as the condenser. Accordingly, a configuration is such that an electromagnetic valve is provided in parallel with the expander in a position upstream of the external heat exchanger and such that the flow rate thereof is ensured by opening the electromagnetic valve (see Reference (1) in the following Related Art List, for instance).